Effect of Corticosteroid Administration on Vasopressin-Induced Adrenocorticotropin Release in Man

The effect of dexamethasone pretreatment on vasopressin-induced corticotropin release in normal human subjects has been studied. Both synthetic lysine vasopressin (L-8-V) and a synthetic analog of vasopressin (CRA-41) were used as corticotropin-releasing substances. Both were found to possess the same degree of corticotropinreleasing activity in the dexamethasone-pretreated subject when administered in equipressor amounts. When 1.5 mg of dexamethasone was given orally at 3:00 pm and 4 pressor units of CRA-41 or L-8-V was administered intravenously at 5:00 pm, the response of the plasma 17-hydroxycorticosteroids was significantly diminished. These data suggested that the response of the dexamethasoneblocked human subject to vasopressin administration differed from that in the experimental animal. The possible significance of these observations as to the site and action of corticosteroid feedback is discussed.